a. Field of the Invention
The present invention relates to the processing of compressed digital data such as MPEG video and, more particularly, to field/frame format conversion of compressed digital data.
b. Description of the Prior Art
Many digital image and video compression standards such as JPEG, MPEG-1, MPEG-2, H.261, and H.263, are based, at least in part, on Discrete Cosine Transform (DCT) coding techniques. DCT coding techniques are one part of MPEG, for instance, that facilitate the efficient compression and thus coding of video digital data. After the video is digitally encoded (compressed) by an MPEG-2 encoder, for instance, it may be desirable or necessary to manipulate or process, generally known as compositing, the data to perform various functions on the resulting, uncompressed video. Such processing may include wipes and dissolves wherein video from a second source is mixed with the video from a first source.
It has been recognized that video compositing in the compressed domain can save computations over compositing in the uncompressed domain by processing less data and reducing the conversion process between compressed and uncompressed data. With the MPEG-2 video compression standard, such processing in the compressed domain equals processing in the DCT domain. Further, MPEG-2 has what is known as mixed field/frame mode macroblocks. Mixed field/frame mode macroblocks improve coding (compression) efficiency. However, at the same time, such mixed field/frame mode macroblocks creates additional computations when it is desired to perform picture compositing. But, in order to perform DCT domain processing with mixed field/frame mode macroblocks, such field/frame conversion is essential.
The conventional prior art approach to field/frame conversion of DCT domain mixed field/frame mode macroblocks performs such field/frame conversion in the spatial domain. This approach requires 2-D (two-Dimensional) IDCT (Inverse DCT) and 2-D DCT processing. Such 2-D IDCT/DCT processing requires a fair amount of time and coding.
It should be understood that field/frame conversion includes field-to-frame and frame-to-field conversion.
It is thus an object of the present invention to provide a simpler approach to field/frame conversion on DCT domain mixed field/frame macroblocks for video compositing.
It is another object of the present invention to provide a non-spatial domain conversion process on DCT domain mixed field/frame macroblocks for video compositing.
It is yet another object of the present invention to provide a 1-D DCT/IDCT field/frame conversion method on DCT domain mixed field/frame macroblocks for video compositing.
It is still another object of the present invention to provide an apparatus for performing the above objects.